Harry Potter and the Methods of Rationality

- and said to Harry, in a strange voice that Draco recognized as how he himself probably sounded to other people, "Beware the green monkey."

"Hsssss ssss sshsshssss," said Harry.

The snake slithered back across the floor to Draco.

"Harry says the message is received and acknowledged," said the shining Blue Krait in Draco's voice.

"Huh," Harry said. "Talking to Patronuses feels odd."

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"Why are you looking at me like that?" said the Heir of Slytherin.

Aftermath:

Harry stared at Draco.

"You mean just magical snakes, right?"

"N-no," said Draco. He was looking rather pale, and was still stammering, but had at least stopped the incoherent noises he'd been making earlier. "You're a Parselmouth, you can speak Parseltongue, it's the language of all snakes everywhere. You can understand any snake when it talks, and they can understand when you talk to them... Harry, you can't possibly believe you were Sorted into Ravenclaw! You're the Heir of Slytherin!"

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"SNAKES ARE SENTIENT?"

Chapter 48: Utilitarian Priorities

It was Saturday, the first morning of February, and at the Ravenclaw table, a boy bearing a breakfast plate heaped high with vegetables was nervously inspecting his servings for the slightest trace of meat.

It might have been an overreaction. After he'd gotten over the raw shock, Harry's common sense had woken up and hypothesized that "Parseltongue" was probably just a linguistic user interface for controlling snakes...

...after all, snakes couldn't really be human-level intelligent, someone would have noticed by now. The smallest-brained creatures Harry had ever heard of with anything like linguistic ability were the African grey parrots taught by Irene Pepperberg. And that was unstructured protolanguage, in a species that played complex games of adultery and needed to model other parrots. While according to what Draco had been able to remember, snakes spoke to Parselmouths in what sounded like normal human language - i.e., full-blown recursive syntactical grammar. That had taken time for hominids to evolve, with huge brains and strong social selection pressures. Snakes didn't have much society at all that Harry had ever heard. And with thousands upon thousands of different species of snakes all over the world, how could they all use the same version of their supposed language, "Parseltongue"?

Of course that was all merely common sense, in which Harry was starting to lose faith entirely.

But Harry was sure he'd heard snakes hissing on the TV at some point - after all, he knew what that sounded like from somewhere - and that hadn't sounded to him like language, which had seemed a good deal more reassuring...

...at first. The problem was that Draco had also asserted that Parselmouths could send snakes on extended complex missions. And if that was true, then Parselmouths had to make snakes persistently intelligent by talking to them. In the worst-case scenario that would make the snake self-aware, like what Harry had accidentally done to the Sorting Hat.

And when Harry had offered that hypothesis, Draco had claimed that he could remember a story - Harry hoped to Cthulhu that this one story was just a fairy tale, it had that ring to it, but there was a story - about Salazar Slytherin sending a brave young viper on a mission to gather information from other snakes.

If any snake a Parselmouth had talked to, could make other snakes self-aware by talking to them, then...

Then...

Harry didn't even know why his mind was going all "then... then..." when he knew perfectly well how the exponential progression would work, it was just the sheer moral horror of it that was blowing his mind.

And what if someone had invented a spell like that to talk to cows?

What if there were Poultrymouths?

Or for that matter...

Harry froze in sudden realization just as the forkful of carrots was about to enter his mouth.